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3 Stage Battery Charger for Lithium Battery

Lithium-ion batteries, being the most common choice, are rightly placed as a power source in most electronic products. As a sustainable energy source, lithium-ion batteries are preferred due to their high reliability, lightweight, more energy density, and lower self-discharge rate.

You may have come across the term “3 stage battery charger for lithium battery” which are also known as “smart chargers” or “micro-processor controlled chargers” in common language. The industry has developed these high-quality chargers as they are efficient in keeping the lithium-ion battery healthy and ensuring the longevity of battery life.

battery charger is using to charge e-bike battery
charging lithium battery after the storage

Are Multi-Stage Battery Chargers the Future?

In order to completely understand the application of lithium-ion batteries, one has to know the basic mechanism behind the charging and discharging process. Understanding this process will ensure safety and optimize lithium-ion battery usage to the fullest.

So you may ask if multi-stage chargers are the future of assisting you with a portable power source or not? Well, these are proving to be a remarkable advancement if we can answer them in simple words.

Firstly, you need to understand how a multi-stage lithium-ion battery charger works. A multi-stage charger relies on its microprocessors and detects the requirement of the battery, thus guaranteeing optimum efficiency in the form of regulated charging. 

The battery charging technology can have multiple stages from 2 to 5. In the first stage, known as the bulk stage, a high level of current charges the lithium-ion battery. However, the trickle charging mechanism is responsible for battery charging in the second stage, known as the absorption stage.

We’ll explain these stages in detail later on when we focus on 3 stage battery charger for a lithium battery.

Capacity, Cycle Life, and Voltage – The Three Elements

There is a close relationship between capacity, cycle life, and voltage used for the charging of a lithium-ion battery. Fluctuation in voltage or capacity issues can have a direct impact on battery life. As the charging cut-off voltage increases, the capacity drops quicker and the cycle life shortens.

Similarly, when the rate of charging increases, it has a direct impact in the form of increased capacity attenuation speed.

charging process of electric bike

How Does a 3 Stage Battery Charger for Lithium Battery Work?

Stage 1 – Bulk Charge

The initial stage involves charging the lithium-ion battery to almost 80 %, wherein the increased voltage is used while the charger current is kept at a constant level. The charger gives as much current to the lithium-ion battery as it can hold. A battery’s absorption rate is the level of current that it can take without overheating.

Charging voltage may differ for different battery types. For instance, in the case of a typical AGM battery of 12 volts, the charging voltage can reach up to 14.6 to 14.8 volts. Similarly, for gel batteries, it’s in between 14.3 to 14.3volts. You’ll be relieved to know that at this stage there is no risk of overcharging as the lithium-ion battery still has the potential to be charged further. 

Stage 2 – Absorption Charge

The absorption stage is where voltage and resistance are measured and detected before charging. Once the milestone of 80 % battery charging is achieved, it’s time for the absorption stage.

Steady voltage is maintained at this stage, contrary to the first one where high voltage is introduced. Meanwhile, amperage is decreased. A low current level keeps the charging going while maintaining safety from overheating levels. 

This stage is more time-consuming as compared to the bulk stage. For instance, 20 % charging at the absorption stage will take significantly more time than the same charging at the bulk stage. Current is constantly in the declining pattern till the lithium-ion battery is fully charged.

Stage 3 – Float Charge

The starting point for this stage may vary for different battery chargers. Few may start this stage at 85 % charging level while others may initiate it at 95 % level.

At this stage, the charge is kept constant at 13 to 13.8 Volts while the reduction in current is made in less than 1 % battery capacity. Voltage is further tapered down at a constant of 13.2 to 13.4 volts until bringing the battery all the way through. For a 12-volt battery, this is the threshold level of voltage. 

You may term it as trickle charger as the current is declined to a maximum level. The float stage is where current is flowing to the battery but at a very low rate which makes it safe for floating for even months without any issue. 

stages of battery charging

Caution for Battery Pack

The condition of the battery pack will add to the performance of rechargeable cells of a lithium-ion battery. You must take care of a few things to ensure the safety and efficiency of the battery pack.

Installation of battery in the battery pack

  • Before assembling the lithium-ion battery into the pack, you should physically inspect the cells
  • You should look for any damaged surface, rust, distortion, electrolyte smell
  • Ensure that different cell types are not used together


  • A dedicated battery charger for the lithium-ion battery is necessary for connecting the battery pack
  • Ensure that the pack can resist external short cut by an inbuild function for safety precautions

Stage battery charging

  • The recommended method for charging is where constant current, as well as constant voltage, are available
  • Maximum charge voltage should be in operation, and the current should be as per the recommendation of the lithium-ion battery manufacturer
  • The operating temperature should be maintained as specified by the battery manufacturer


  • The method for discharging is in the operation of constant current
  • Maximum discharge current should be used for discharging as specified by the battery manufacturer
  • Discharging should be done under operating temperature as specified by the battery manufacturer

Final thoughts

We’ve said all and we’ll say it again, 3 stage battery charger is the smartest thing to charge your lithium-ion batteries. Simply put, these are the handiest and most efficient pieces of charging equipment that your batteries need. You don’t have to worry about anything.

You don’t have to worry about the continuous connection of the battery charger for fear of overcharging etc. Battery-powered equipment should be connected with a 3-stage charger, especially in the off-season when they are kept in storage.

We recommend you to check at cool battery products available at Tritek Battery which we are pretty sure is what you are looking for. They offer original custom designs of batteries for customers’ applications, several types of ready-made e-bike batteries and smart chargers as well.

Keep in mind, that the healthiest stage of the battery is the one where it’s fully charged.

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Picture of Bluen Lee

Bluen Lee

Hello, I'm Bluen, I have over 25 years in the battery industry.
Throughout my career, I've developed a deep understanding of the battery market and kept up with the latest trends in R&D.
I'm excited to share my insights and knowledge with you through my blog.


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Tritek is your ODM partner for lev battery, and we pay close attention to your requirements.

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Customized exclusive battery

Shenzhen Tritek Limited is the most professional lev battery manufacturer in China. working with the world-leading companies for intelligent lev and electric drive systems.

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Tritek is your ODM partner for lev battery, and we pay close attention to your requirements.

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Tritek aim to be the world leading supplier of the lev battery

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